Tweaked the unset primary key check from [5933] to accommodate models…

… created in the oldforms style. It's a backwards-compatibility hack that we can remove when oldforms go away. See #2160 for discussion. Fixed #5204, #2160. Refs #5102.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5934 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/base.py

@@ -209,7 +209,9 @@ def save(self, raw=False):
 
         # First, try an UPDATE. If that doesn't update anything, do an INSERT.
         pk_val = self._get_pk_val()
-        pk_set = pk_val is not None
+        # Note: the comparison with '' is required for compatibility with
+        # oldforms-style model creation.
+        pk_set = pk_val is not None and pk_val != u''
         record_exists = True
         if pk_set:
             # Determine whether a record with the primary key already exists.